Measurement-based stochastic models for channel transition in underground subway environments

In this contribution, a recently conducted measurement campaign in underground subway environments is introduced. The downlink signals in an in-service UMTS network are collected in the subway carriage by using an Universal Software-defined Radio Peripheral (USRP) equipment and used to extract the channel impulse responses (CIRs) between a user equipment and UMTS stations. A high-resolution parameter estimation algorithm derived based on the SAGE principle is applied to estimate the delays, Doppler frequencies and complex attenuations of multiple propagation paths from the CIRs. Based on the multipath parameter estimates, the composite delay and Doppler frequency spreads are calculated. Significant transitions are observed for the channels when the subway increases its speed moving from a platform to a tunnel. The statistics of the time-variations of the aforementioned parameters during the transitions are extracted which constitute a stochastic model for channel transitions in underground subway environments.